Actually, round to even would be correct for numbers ending in .5

This is new to me, up to now I always rounded .5 up. But you seem to be right, e.g. Mathematica rounds in that way. The reason for this is that the rounding should not give a statistical bias - as far as I understand it.

But in this case, 1.025 really is closer to 1.02 printf "%.20f => %.2f\n", 1.025, 1.025;
# this prints
1.02499999999999990000 => 1.02

[download]
D'oh, well, been tripped up again by floating point number representations (tye explains that very nicely here in this thread) ...

What is interesting is the following example where the rounding towards the nearest even number (0) does not take place - and the 0.5 can be represented exactly as a float (as merlyn pointed out somewhere else in this node): 

printf "%.20f => %.0f", 0.5, 0.5;

# prints
0.50000000000000000000 => 1

[download]

-- Hofmator

In reply to Re4: Filthy Floats by Hofmator
in thread Filthy Floats by THuG

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